The preferred embodiment concerns methods and devices for control of an electrographic printer or copier as well as an electrographic printer or copier.
Known electrographic printers or copiers comprise a plurality of sensors (such as, for example, light barriers and switches) to monitor the paper path. Furthermore, these known printers contain a plurality of actuators such as, for example, servo motors, step motors, valves and solenoids, whereby at least with some actuators the servo position of the actuator is monitored with the aid of a position feedback. The paper path of a single sheet to be printed by the printer is controlled with the aid of the actuators and monitored with the aid of the sensors. Furthermore, the sensors are used in order to control between successive single sheets to be printed and to determine control time points. Thus in known printers or copiers at least one light barrier is arranged directly in front of a printing group in order to start the printing process of the printing group when the leading edge of the sheet has reached the light barrier. It should thereby be achieved that the print image is correctly transfer printed on the supplied side of the single sheet.
To establish a paper jam, in known printers it is monitored how long a sensor signal that is triggered by a page present in the sensor region is present. If this time exceeds a predetermined limit value, it is assumed that the paper is jammed in the region of the sensor. In known printers or copiers, the time that a single sheet needs after passing a first sensor until arriving at a second sensor is also recorded. If this time exceeds a preset limit value, it is assumed that the single sheet is still located between the two sensors and a paper jam has occurred. In known printers or copiers, the actuators are activated according to a control schema dependent on sensor signals.
Depending on the operating type of the printer or copier, a predetermined sheet separation is to be set between successive single sheets to be printed. To set the sheet separation, the sheet separation between two single sheets is measured, whereby given a deviation from a preset sheet separation the sheet separation for subsequent single sheets is controlled dependent on the deviation. Thus a plurality of time observations of single sheets is controlled dependent on the deviation. In these known printers or copiers, a plurality of time observations of relative times are thus necessary that intervene in the individual control workflows and are provided by the controllers of the structural groups of the printer or copier. In particular in high-capacity printers and high-capacity copiers with a printing or copying speed of ≧50 sheet DIN A4 per minute with a plurality of paper paths, a plurality of sensors and actuators are necessary in order to ensure both the high printing speed and a high print quality. Very elaborate and powerful controllers are in particular necessary for these high-capacity printers copiers. Further sensors are necessary in order to further improve the print quality of these printers or copiers and primarily in order to further increase the printing speed, whereby the evaluation of the sensor signals must occur with a higher precision with increasing printing speed of the printer or copier. However, these complex control tasks are only to be realized with a significant effort.
Such known high-capacity printers are, for example, specified in the international patent applications WO/18054 and WO98/18052, from which a high-capacity printer with two printing groups for printing of single sheets is known. The described printers can be operated in at least two operating modes, whereby the transport path of the single sheet through the printer is established by the operating mode. The printers have a plurality of sensors and actuators for control of the paper transport and of the printing process.